The examination of the battery on a Japan Airlines Co. 787 that caught fire in Boston a month ago shows a failure in a single cell spread to the rest of the battery, causing it to overheat in an uncontrolled way, National Transportation Safety Board Chairman Deborah Hersman said in Washington today.
Boeing had said its tests showed no evidence such a cascading failure was possible, and assessed that the lithium-ion batteries would produce smoke less than once in 10 million flight hours, Hersman said.
“The 787 fleet has accumulated less than 100,000 flight hours, yet there have been two battery events resulting in smoke less than two weeks apart and on two different aircraft,” she said. “Assumptions used to certify the battery must be reconsidered.”
Investigators and Boeing are trying to determine what caused a battery fire on the JAL plane in Boston and a cockpit warning that spurred an emergency landing in Japan by an All Nippon Airways Co. 787. Those incidents triggered grounding orders worldwide starting Jan. 16.
The NTSB has found one cell on the JAL battery overheated as a result of a short-circuit, starting a reaction in other cells that led to the fire, Hersman said. Investigators still are looking at possible causes of the initial short-circuit, including the recharging process, she said.
There was an unexpected drop in the battery voltage to 28 volts from 32 volts, pointing to the failure of one of the battery’s eight cells, she said. Investigators ruled out mechanical damage and external short-circuiting. All battery damage occurred after the short-circuiting began, she said.
The board’s next steps are to examine how the battery was charged, its design, how the cells are linked, the way they’re separated and how it was manufactured, Hersman said.
“We are working collaboratively to address questions about our testing and compliance with certification standards, and we will not hesitate to make changes that lead to improved testing processes and products,” Marc Birtel, a spokesman at Boeing’s commercial headquarters in Seattle, said in a statement.
Clarifying comments made yesterday about the agency being “weeks away” from providing answers to what happened and needed changes, Hersman said the board would release an interim factual report in about 30 days. It will summarize everything the NTSB has learned, while it won’t signal the probe is over, Hersman said.
“You’re coming closer to circling what the problem is,” Howard Rubel, an analyst with Jefferies & Co. in New York who has a “buy” rating on Boeing, said in a telephone interview after the press conference. “They have identified the origin of the battery fire. You’re eliminating uncertainty. Once you know where, you can usually find the why. Before, we didn’t even know where the where was.”
Boeing rose $1.14, or 1.5 percent, to $77.43 at 4 p.m. in New York trading.
The Federal Aviation Administration, not the NTSB, will decide when to let the Dreamliner resume flights, Hersman said.
The FAA hasn’t finished its probe of the Dreamliner’s certification and manufacturing processes or reached conclusions about what changes may be needed, Transportation Secretary Ray LaHood and FAA Administrator Michael Huerta said in a joint statement today.
“We are working diligently with Boeing to figure out the problem and to find a solution,” Huerta said in prepared remarks for a speech today in Salt Lake City. “Our goal is to get this done as quickly as possible, but we must be confident that the problems are corrected before we can move forward.”
The agency allowed Boeing to make one flight with a Dreamliner today, under the condition that only the crew would be on board, that special checks of the battery and system would be performed, and that the jet would land immediately if there were any indications of a battery fault. The plane landed by Boeing’s wide-body factory in Everett, Washington, at 10:56 a.m. local time, according to FlightAware’s live flight tracking.
Pilots “monitored the battery status page throughout the flight and indicated that the flight was uneventful,” Boeing’s Birtel said.
The lithium battery packs are an essential component of the Dreamliner’s advanced design, which was developed to conserve fuel. The 787 uses five times more electricity than similar jets and its fuselage and wings are made from composite materials that are lighter than aluminum.
Because FAA regulations didn’t cover aspects of the new design, the plane was certified with “special conditions,” including nine that allowed use of the lithium-ion batteries, Hersman said.
Boeing received regulators’ permission to use the batteries in 2007, three years after the FAA barred passenger planes from carrying non-rechargeable versions of that type of battery as cargo because of fire concerns.
Boeing’s chief engineer, Mike Sinnett, said Jan. 9 that the batteries were designed so that single-cell failures wouldn’t cascade to the others, and that the plane would be safe even if they did. He said there had been no issues with the battery cells over 1.3 million operating hours.
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